In preparation for reinforcing rubber with textile cords, it is customary to topcoat the cords first with RFL (resorcinol-formaldehyde-latex) compositions in order to improve adhesion of the cords to the rubber. The applied RFL topcoat is only partially cured before embedment in rubber. This approach is very effective for nylon cords. For cords of many other polymers, e.g., polyethylene terephthalate, it is desirable to subcoat the yarns first with a material that enhances adhesion of the RFL topcoat to the cords. This is often referred to as adhesion activation.
High modulus, high tenacity aramid yarns as described, for example, in Blades U.S. Pat. No. 3,869,429, issued Mar. 4, 1975, and Shimada et al. U.S. Pat. No. 4,355,151, issued Feb. 26, 1979, are outstandingly effective for rubber reinforcement. It has been found that cords of such yarns do not exhibit adequate adhesion to rubber when coated only with RFL. Adhesion activation is required such as described in Research Disclosures 13730 (September 1975) and 13347 (May 1975). Generally these involve a subcoat of partially cured epoxy resin followed by an RFL topcoat.
This invention provides a system which enables the yarn producer to adhesion activate his aramid yarns. The rubber goods manufacturer needs apply only a single RFL dip to the reinforcing cords before embedment in rubber, as in tire applications.